His pitch for a 30% tax on people who earn $1 million or more a year reinforces differences with likely Republican rival Mitt Romney.

Standing with millionaires and their assistants, President Obama makes… (Chip Somodevilla / Getty…)

WASHINGTON — President Obama plugged his plan to increase taxes on the wealthy yet again Wednesday, but this time with a new twist — appearing alongside rich people who support his so-called Buffett rule.

The proposal has become a favorite political theme for the president, who touted it in a speech last week, then again at events in Florida on Tuesday.

The proposal would require that people with annual incomes of $1 million or more pay at least 30% of their income in federal taxes. Democratic strategists believe the idea has a strong political punch — particularly now, when many Americans are filing their taxes — and taps into the widely held belief that the U.S. economy and political system tilt in favor of the wealthy.

Repeatedly raising the Buffett rule also serves to remind voters that Mitt Romney, the presumed Republican presidential candidate, paid 14% of his income in taxes last year. Romney, like many wealthy Americans, benefited from the fact that investment income gets taxed at a lower rate than wages.

Democratic leaders have scheduled a vote in the Senate for Monday on an effort to bring the Buffett rule up for consideration. Republican senators are expected to block the move.

Republicans say the proposal is based on faulty economics. Raising taxes on the wealthy won't do anything to create jobs, GOP critics argue, nor will the Buffett proposal contribute in any substantial way to reducing the federal budget deficit.

"He's really trying to divert from the failure of his record, which is that he has not created jobs," Romney said Wednesday on Fox News. "He has lost 800,000 jobs during his presidency."

Still, the topic makes GOP lawmakers dyspeptic because it gives Obama the chance to speak directly to independent voters about kitchen-table issues. And he repeatedly portrays the Republican Party as concerned with the problems of the wealthy, not the middle class.

The rule is named for billionaire investor Warren Buffett, who has famously complained that he pays a lower tax rate than does his secretary.

To help make the point, several wealthy Americans showed up to endorse the Buffett rule — along with their assistants — and appeared on stage with Obama. None of the millionaires were actually excited about paying more taxes, Obama said.

But "they agree with Warren," he said. "This should be fixed."

The measure is highly unlikely to pass the divided Congress this election year. But the event was live on cable television Wednesday, same as the day before, giving the president's message the kind of exposure money can't buy.